Julian Miles QC represented three media organisations at a hearing in the High Court at Auckland on Friday and less than 24 hours later spoke at the World Bar Conference in Queenstown.
Mr Slater had sought an injunction stopping further publication of private emails hacked from his computer.
The emails have caused a storm of controversy during the past three weeks, leading to the resignation of Minister of Justice Judith Collins.
On Friday, Mr Slater won an interim injunction against ''unknown defendants'' publishing his private emails - referring to the hacker known as Whaledump, or Rawshark, who obtained the information used as the basis for Nicky Hager's controversial book, Dirty Politics.
But Justice John Fogarty said Mediaworks TV, The New Zealand Herald and Fairfax could run what material they already had. Mr Slater is also being sued by Auckland businessman Matthew Blomfield in a defamation case.
Mr Slater resisted handing over information about sources by trying to claim the same legal protections as journalists - but a district court judge in December rejected the position.
''His Honour argued blogging was not journalism and hence the defendant, a well-known blogger under the name of Whale Oil, had to reveal his sources,'' Mr Miles said in his Queenstown speech on Saturday.
''Now in the High Court that ruling was challenged - the judgement is yet to be delivered.
''I was involved as an amicus [lawyer not directly involved who advises the court]. I think it's likely that the district court ruling will be overturned and the protection extended to journalists who blog and blogging.''
Mr Miles was speaking at the timely session at the three-day conference ''Surveillance versus privacy; the balance between the State, the Fourth Estate, the citizen and the rule of law''.
The privacy and media law expert gave a colourful potted history of the recent surveillance and privacy issues - from the Five Eyes surveillance programme, the Edward Snowden revelations and the Dotcom mansion raid to interception warrants, the handing over of phone records and movement data of journalist Andrea Vance to a Government inquiry, and the Whale Oil saga.
Also speaking at the session were award-winning International Human Rights lawyer Beatrice Mtetwa, of Zimbabwe; Chief Judge Alex Kozinski of the United States Court of Appeals for the Ninth Circuit; and Justice Robert Jay QC, counsel to the Leveson Inquiry into phone-hacking by the British press and to the Crown in a number of torture and national security cases.
